No, it's not rocket science, but you won't learn how to do it overnight, not even in a year. If you start to dedicate yourself to doing your own SEO, you will most likely harm your positioning and end up in a worse position than before. In my experience, if you follow a solid learning plan and make the necessary effort, you can learn the basics in less than 6 months. For example, it will be much easier for a web developer to make the transition to SEO than for a physical worker who has absolutely no technical knowledge.
The reason why I've set 6 months as a minimum period is that SEO takes time to work and you may have to wait a couple of months (or more) to see the impact of SEO-related changes on a website. It's possible to learn to do SEO on your own, you don't have to be an SEO specialist or expert. The amount of free SEO resources, websites, books, videos, or podcasts is so large that you don't really need to spend money to learn SEO and be a great SEO (at least at first). Therefore, SEO is not the same as paid advertising and it's not the only component of search engine marketing.
Be prepared to spend even a couple of years learning and experimenting before trying to make SEO your well-paid day job. There are more than 255 SEO ranking factors to consider when optimizing a website and, for ease of reference, they are divided into several sub-processes. Learning the theory behind SEO is crucial to understanding how SEO works and understanding its basic concepts. You're reading about successful SEOs that learn six figures a month and you see yourself doing it in a couple of months.
The best way to learn SEO in a practical way is to set up your own website just for the purpose of learning SEO. A high-quality course will help you understand SEO without having to spend endless hours searching for this information in random resources on Google. During this period, you'll spend most of your time practicing SEO and not just reading theory. Fortunately, my 8 years of experience have taught me to distinguish between high-quality SEO resources and low-quality SEO scams.
If you want to learn SEO just because you've heard that you can make a lot of money doing it and that it's a very fashionable profession, then don't.